1. Field of the Invention
The present invention relates to a compression connector for use with electrically conductive wires having a stranded center conductor.
2. Prior Art
A variety of methods are currently employed for attaching the stranded center conductor of a wire to a terminal. Most methods require that a portion of the jacket covering of the wire be stripped to expose a portion of the stranded conductor. The stripped portion of the wire is then inserted into the hollow sleeve of a connector such as a spade lug and radial pressure is applied to the sleeve with a crimping tool to prevent longitudinal force from pulling the wire from the connector. This is similar to the standard crimp type connections used on cars, boats and trailers. The limitation in these designs is that a stranded wire conductor has spaces between strands, even after compression. Over time, such spaces between strands can be easily reduced after compression, such as by vibration or corrosion, which reduces the outer diameter of the stripped, crimped portion of the wire. The strands of the wire will move to fill the void resulting in the initial crimp or radial force originally applied to hold the wire being inadequate to continue to securely hold the wire.
Holliday, in U.S. Patent Application Publication No. 2005/0159041 discloses a fitting which is adapted for connecting a stripped end of an electrically conductive wire to another electrically conductive member. The fitting includes an adapter having a hollow, generally cylindrical body which is open at one end, an internally threaded wall portion in the body which is dimensioned to receive and to threadingly engage the stripped end of the wire, a connector body including a connector sleeve into which the adapter is inserted, and means for crimping the adapter into positive engagement with the wire. A plurality of adapters are provided for each connector assembly in which the internally threaded wall portions are sized to match up with a different gauge wire but wherein the outer diameters of the adapters are the same in order to use the same or consistent size connector body for the different gauge wires. The adapters are further characterized by being slotted to form arcuate segments at the entrance end of the adapter for insertion of the wire, the slots being dimensioned to limit the inward radial contraction of the segments into clamping engagement with the end of the wire. A problem with this fitting is that it requires a separate loose cap for the assembly that can be easily lost. In addition, different sizes of wire require a separate adapter requiring identification. A further disadvantage in this type of fitting is that if the strands of wire comprising the conductor undergo corrosion, tension on the wire may cause the stripped portion to pull out of the adapter and, accordingly, the fitting. This disengagement can happen because the trapped strands of wire are parallel to both the axis of the adapter and the direction of the unstripped portion of wire.
Korte et al., in U.S. Pat. No. 6,857,895, disclose an electrical connector for coupling to a multi-stranded conductor. The electrical connector can be used for coupling to an insulated multi-stranded conductor. The connector includes a housing having at least one bore for receiving an insulated multi-stranded electrical conductor; an electrically conductive prong located in the bore and electrically connected to the housing; and a securing means for insertion into the bore after insertion of the electrical conductor into the bore and onto the prong. Insertion of the securing means into the bore, after insertion of the electrical conductor into the bore and onto the prong, presses the strands of the electrical conductor against the conductive prong such that the connector makes electrical contact with the electrical conductor and acts to mechanically secure the electrical conductor to the connector. A limitation and disadvantage of the connector of Korte et al. is that the prong is funnel-shaped and when lateral pressure is exerted on the cable jacket during the compression step, the lateral forces (directed radially inwardly) tend to force the stranded wire rearwardly (i.e., off of the prong) due to the conical shape of the prong, and rearward tension on the cable may separate the cable from the connector.
In the connector of Korte et al., the unstripped cable is pushed onto a smooth prong whose diameter changes with a sloped design. As a rear plug is moved inwardly to lock the cable into the connector, the space between the fixed outer shell and the sloped center prong is reduced by the addition of a wedge-type action of the plug. The limitations of this design further include the need to assure the wire is pushed forward sufficiently onto the sloped prong to result in the required holding force, the stranded wire slipping rearwardly off of the smooth surface of the prong as the connector is being handled and compressed, and that the strands remain in the same plane as the pulling force. The holding power relies on wire being inserted to the correct depth as well as the exact sizing of the plug and body to a limited size of wire. In addition, the insertion of the rear plug must be complete to effect the designed holding and whose forward motion could be limited by the stranded wire not aligning directly onto the prong and sitting on one side. This would not allow the plug to be fully inserted.
In view of the aforementioned limitations of the prior art stranded conductive wire cable connectors, it would be an advance in the art to provide a one-piece compression-type connector for a wire having a stranded conductor wherein the trapped strands of wire resist separation from the fitting when tension is applied to the wire, even when the strands are corroded.